Self-folding flat-pack robots walk into our future

Rachel Feltman

Thanks to the ancient art of paper folding, a little scientific ingenuity, and a whole mess of Shrinky Dinks, researchers have designed flat paper robots that can fold themselves into 3-D shapes and walk away. Their results, published on Thursday in Science, point to a future of self-assembling bots that can be built and transported at lower costs than traditional robots, as well as used in tighter spaces. And their paper isn't even the only origami-inspired innovation in Science this week.

Why origami? In the past couple of decades, mathematicians and artists alike have been pushing the boundaries of the practice. Now we have computer programs that can figure out the folding pattern to create basically any design. These simulations have revealed that paper folding produces some interesting mechanical properties, and engineers have taken note.

These new robots are made of paper layered with Shrinky Dinks, a plastic (sold as a children's toy) that shrinks when heated. The researchers snaked circuits into the plastic in the spots where they wanted the robot to bend as it assembled. When the circuits heat the plastic, the robot is pulled into its final shape. With the help of a motor and battery, it then walks away.

Of course a motor and battery mean that the bot is never truly flat. And the thickness of the paper sheets, while only a few millimetres, limits the flatness of the robot as well. But Sam Felton, a PhD candidate at Harvard University's School of Engineering and Applied Sciences and the Wyss Institute for Biologically Inspired Engineering and the study's lead author, is confident that flat electronics will be easier to come by soon.

"People are already 3D printing batteries that are very flat," he said. "We'll eventually have options for creating 2D versions of all the components we need." And while this robot can only fold itself into a single shape, different materials could hypothetically produce a more versatile model.

And some of those materials are already on the way: In another study published in Thursday's Science, researchers report on their work creating novel new materials inspired by origami.

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"A single sheet of paper has certain properties, but when you fold it into a particular pattern, it suddenly has new properties," co-author and University of Massachusetts Amherst physicist Christian Santangelo said. "So the idea is that you could use paper folding to make new materials, and ones with the properties you want - even if they aren't found in nature."

In one example, Professor Santangelo said, the team – a large group made up of scientists from Cornell University, the University of Massachusetts, Western New England University and Amherst – created a folded material with little points that could be "popped" in or out individually.

Inspired by the traditional Japanese art form of Origami or "folding paper," researchers have developed a way to coax flat sheets of composite materials to self-fold into complex robots.

"We found that you could take one of these bits and pop it into the opposite direction, and it changed the mechanical properties," Professor Santangelo said. A line popped in one direction became a hinge, while popping the same line of points in the opposite direction created a rigid, fixed line.

But like the first team of researchers, Professor Santangelo and his collaborators have robots in mind. "Robotics is definitely the most obvious use," he said. "Imagine having a robot that could decide to turn a rigid piece into a fold, and just create an elbow whenever it needs one."

Lead author Jesse L. Silverberg, a graduate student in physics at Cornell, suggested that folded paper materials might have a place in soft robotics. An increasingly popular field, soft robotics creates robots that are made entirely with flexible materials. Without hard edges, they can move into tight spaces with unique flexibility.

"Imagine this: a building collapses, and you have a snake-like robot that can go into debris. And as it unfolds, it goes from a soft robot to a rigid barrier that could protect people," Dr Silverberg said. "It folds one way to crawl into tight spaces, and another way to become a protective barrier. It can transform its function on the fly."

Dr Felton, lead author of the first study, suggested space as the perfect destination for flat-pack robots: The ability to pack many robots into a small space would make their delivery more fuel-efficient.

The two research groups are definitely aware of each other, and collaboration isn't out of the question. "The bottom line is that the potential applications of paper folding are just really cool," Dr Silverberg said, "and I think it's safe to say that the future is going to be awesome."